SiC can be used not only as a component modifier but also for cost reduction. In this study, the effects of SiC on the mechanical properties of flake graphite cast iron were investigated by changing the purity and amount of SiC. The addition of SiC to chilled pure pig iron was found to be ineffective because SiC promotes the crystallization of D-type and E-type graphite and decreases the strength of cast iron. However, it is possible to promote the crystallization of A-type graphite according to the type of inoculant. The molten metal treatment is known to be effective for promoting the crystallization of A-type graphite and increase tensile strength, by raising the final solidification temperature. The results of this study showed that when non-chilled pig iron is used, the addition of SiC is effective in terms of both cost and material.

  Use of casting CAE is effective for preventing and countermeasuring casting defects. However, this method is ineffective for predicting defects caused by sand mold characteristics, because casting CAE treats the actual mixture of sand particles and air in the sand mold as one continuum material, thus the correspondence between the essential sand mold characteristics and thermophysical properties of the mold in unclear in numerical analysis.

  In this study, we investigated a method for predicting penetration defects by mold filling, heat transfer, and solidification analyses using a casting CAE software. First, the differences in sand mold characteristics were identified based on the thermophysical properties of the mold material in casting CAE. Next, the relationship between some cooling curves obtained by numerical analysis and the presence/absence of penetration defects observed in casting experiments was investigated, and the conditions for the occurrence of penetration defects were determined. In the present study, penetration defects occurred at a mold surface temperature of 1310 °C or higher for 5s or longer after mold filling was completed. This condition was verified with eight types of molds and the results showed that the proposed method is effective for determining the existence of penetration defects..

  Generally, high iron contents in Al-Si system alloys tend to coarsen Al-Fe-Si compounds. However, in the preliminary experiments of this study, the compounds in the die castings made of Al-17.8%Si-4.4%Cu-0.5%Mg-1.9%Fe-0.9%Mn-0.01%P alloy were found to be fine. Gravity casting experiments were conducted using high iron containing hypereutectic Al-Si alloys whose trace elements (phosphorus and strontium) were controlled to change the melt undercooling during the crystallization of the primary silicon. As a result of microstructure observations and thermal analysis, it was found that the compounds tended to be finer as the degree of melt undercooling increased. The refining mechanism of the compounds is discussed as follows. (1) It is assumed that when a primary silicon crystal solidifies in a highly undercooled melt, the concentration of silicon decreases and that of iron and manganese increases in the melt in the front of the primary silicon surface. (2) According to the assumption (1), the crystallization temperature of the compound is thought to rise near the surface of the primary silicon. (3) These two factors (namely, the melt undercooling during the crystallization of the primary silicon and the rise of the crystallization temperature of the compound) are thought to cause the constitutional undercooling that serves as the driving force refining the compounds.